Many of us grew up with the message that milk is the champion of bone health thanks to its rich calcium content. However, today, a misconception continues to gain traction – that calcium from milk isn’t absorbed by the body, while the calcium from vegetables is superior. Therefore, a vegan diet is better due to calcium nutrition, among other reasons. This article debunks this myth and explores why milk remains a valuable source of calcium for people of all ages.
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Bioavailability of Calcium From Milk
The amount of calcium in a food does not tell you how much will be absorbed by your body. It is true that the calcium from milk is not absorbed 100%. The ability of a nutrient to be absorbed is called its bioavailability. Calcium in all forms of milk has about 30% bioavailability.
Since milk has around 300 mg of calcium per cup, this means that around 90 mg will be absorbed by the body.
In reality, there is no single food from which the calcium is absorbed 100%. The same is true of any mineral. However, some vegetables do contain calcium with a higher rate of absorption. Let’s look at the calcium content of some common foods together with the calcium bioavailability, starting with milk.
In this post, we are concerned with comparing milk to vegetables. Other dairy products will have lower or higher calcium amounts. However, the bioavailability will be the same or about the same, meaning that there is no point in comparing every dairy product.
Calcium Availability of Select Foods
| Food | Amount | Calcium Amt. (mg) | Calcium Bioavailability |
| Milk | 1 cup | 300 | 30% |
| Broccoli, cooked | 1 cup | 180 | 50-60% |
| Kale, cooked | 1 cup | 354 | 49% |
| Spinach, cooked | 1 cup | 245 | 5% |
| Bok Choy, cooked | 1 cup | 158 | 54% |
| Brussels Sprouts, cooked | 1 cup | 56.5 | 63.8% |
| Green Cabbage, cooked | 1 cup | 72 | 65% |
| Orange Juice, unfortified | 1 cup | 99.5 | 36.3% |
| Almonds, roasted | 1 cup | 370 | 21.2% |
| Pinto Beans | 1 cup | 175 | 26.7% |
The amount of calcium and the absorption of calcium varies per vegetable, nut, or legume. Some have very very low absorption and some have much higher absorption than milk.
Broccoli, for instance, has around 60% absorption while milk has 32%. This means that, on average, you will get 90 mg of calcium from one cup of milk and around 108 mg from one cup of cooked broccoli. Let’s compare the estimated amount of absorbed calcium from the foods above given the same amounts.
Estimated Calcium Amount From Select Foods
- Milk: 90 mg
- Broccoli: 108 mg
- Kale: 173 mg
- Spinach: 12.7 mg
- Bok Choy: 85.9 mg
- Brussels Sprouts: 36 mg
- Green Cabbage: 46.8 mg
- Orange Juice: 36 mg
- Almonds: 78.4 mg
- Pinto Beans: 46.4 mg
Milk and dairy products contain more calcium than most green vegetables. Very high absorption rates from some foods fail to outweigh low content. While kale is a standout source of calcium in this list and broccoli provides a moderately higher amount of calcium, all the other foods provide much less calcium than milk.
Many other foods could be added to the list and the results will remain consistent. While there are some foods that will provide more calcium than milk, most will provide around the same amount or less, sometimes much less. So, milk and dairy products are still a very good source of calcium compared to any other food.
Why Do Some Plant Foods Have Such Low Calcium Availability?
You’ll notice from the list above that spinach has a very low calcium bioavailability of only 12.7%. This is because spinach is high in oxalates. Oxalates are anti-nutrients that can bind to calcium and decrease its bioavailability.
Another high-oxalate food is rhubarb. One cup of cooked rhubarb contains around 348 mg of calcium but its bioavailability is only 8.5, leading to a dismal amount of calcium delivered, at 29.6 mg. Beets are also very high in oxalates, or oxalic acid.
Phytates, or phytic acid, the storage form of phosphorus, also interfere with calcium availability. Legumes like pinto beans are high in phytates but so are many other common plant foods like grains, nuts, seeds, and some root vegetables. Even if you eat a cup of almonds, which is more than we normally eat, you get less calcium than from a cup of milk.
While you should avoid filling your diet with a preponderance of high-oxalate foods, in general, all this means is that we never get a free lunch. Even in nutrition, you can’t get something for nothing! Milk is a very good source of calcium but you do not need to rely on it, just know that you need a variety of plant-based foods to get enough calcium in your diet and some vegetables are low in calcium, in terms of amount or bioavailability.
Does Protein Leach Calcium From Bones?
Another milk and calcium claim is that the high protein content from milk makes it bad for your bones because of protein metabolism. The claim is that protein “leaches calcium from bones.”
This is a gross exaggeration and there is NO evidence of it! Diets high in protein do tend to coincide with an increase in calcium excretion in the urine, but there is no data to indicate that this causes bone demineralization or any harmful effect on bone health as long as calcium intake is adequate.
On the contrary, high-protein diets may increase the absorption of calcium. Milk is a good source of calcium. Calcium is essential to your bones. Milk will not harm your bones but will give you an abundant supply of calcium.
In summary, you do not need milk to get adequate calcium from your diet, but a vegan diet is not superior to milk and dairy in terms of calcium nutrition.
Key Summary Points For “Calcium from Milk Is Not Absorbed By the Body?”
- While many people have long believed that milk is a champion of bone health thanks to its high calcium content, a modern myth continues to gain traction: That the calcium from milk is not absorbed by the body and the calcium from plant foods is superior.
- Calcium in milk has about a 30% bioavailability, meaning around 90mg of the 300mg per cup will be absorbed by the body.
- Some vegetables like broccoli and kale have higher calcium bioavailability, but most green vegetables provide much less total calcium than milk.
- The calcium absorbed from milk compares favorably to great calcium sources like broccoli and kale, while providing much more calcium than spinach, bok choy, brussels sprouts, green cabbage, and other plant foods.
- Foods high in oxalates and phytates can reduce the bioavailability of calcium as oxolates and phytates bind to calcium and prevent its absorption.. Therefore, you don’t get the full calcium content from these foods.
- Since milk is high-protein, it is claimed to leach calcium from bones, therefore reducing or eliminating its value as a calcium source. This is a myth.
- High protein diets do not cause bone demineralization as long as calcium intake is adequate. Therefore, milk is a good source of both calcium and protein for bone health.
